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Will Your Flu Shot Protect You Against Swine Flu?

The U.S. Centers for Disease Control and Prevention strongly doubts that this year's flu vaccine will offer people any protection from the swine flu. "We don't think that any of the existing vaccines are effective," acting CDC Director Richard Besser said yesterday at a press conference.

But some flu vaccine researchers and public health experts say the jury is still out. "If I hadn't already had the vaccine, I'd take it," says Robert Webster, a flu guru and vaccinemaker at St. Jude Children's Research Hospital in Memphis, Tennessee.

CDC's Daniel Jernigan says experiments with ferrets done there suggest that the current vaccine has no power against the H1N1 strain of swine flu now circulating the globe. CDC researchers took ferrets never infected with an influenza virus and injected them with this year's vaccine, which has an H1N1 component of human, not swine, origin. They then tested the ferrets' blood sera, the part that contains antibodies triggered by the vaccine, against the swine H1N1 from the outbreak. "The sera do not provide any protection," says Jernigan.

Then again, as Jernigan acknowledges, antibodies provide only one type of immunity triggered by the vaccine.

The vaccine can also stimulate the cell-mediated arm of the immune system, the part that clears infected cells from the blood. The ferret model did not further test the possibility that vaccination leads to milder disease. And many elderly people may also have some immunity from previous infections with similar influenza viruses or previous vaccinations. "There's a lot of information that we don't have," says Jernigan.

Julio Frenk, dean of Harvard School of Public Health in Boston and the former secretary of health in Mexico, like Webster, suspects that the vaccine may do some good. Frenk notes that Mexico has excellent vaccine coverage of children under 5 years old and the elderly, the two groups that have been spared in this outbreak. "There's a likelihood that there's at least partial protection," says Frenk, who was in Mexico City at the time.

Webster, who says he wouldn't expect much from the current vaccine because the H1N1 in it differs markedly from the new strain, still says it may make the difference between developing a mild illness and death.

You can find our full coverage of swine flu--including breaking news on the latest developments--here.